Over the years, many types of hitching assemblies have been developed for a variety of purposes. With each it is necessary that the implement or plow be towable and with some, the hitch will move the implement between a raised transport position where the implement is out of contact with the soil and a lowered working position. When in the raised transport position, it is most desirable that the implement or plow be as fixed or secure as possible with respect to the tractor to which the implement and hitch are attached to ease transportation and to minimize the potential of injury from swaying or movement of the implement through a horizontal arc. It is also desirable to control raising and lowering from the tractor operator's position on the tractor. On the other hand, when plowing it is most desirable that the plow be highly maneuverable behind the tractor so that regardless of the direction the tractor takes, the plow will follow.
Additionally, it is important for the plow to be kept in its plowing attitude while at the same time being able to successfully avoid impediments, obstacles or hazards in the earth that might otherwise damage the plow. While it is important to avoid such impediments, it is also desirable that the plow be returned to its plowing position once the obstacle has been passed by so that plowing can resume.
Thus, the primary objective of the hitch assembly is to provide a hitch useful with a wide variety of tractors and one that can be adapted to a variety of models or types of implements or plows, one that will allow attachment and hook up, as well as manufacture with the least amount of effort and cost. It is also desirable to provide the most amount of clearance between the lowest point of the plow and the ground when the plow is in its raised or transport position. It is also an important objective to provide an easily operable hitch, one that can be safely locked and unlocked, especially without requiring the operator to get off the tractor to perform either the locking or unlocking functions and a hitch that will positively prevent horizontal movement of the hitch and any attached implement when in its raised position.
With respect to the fireline plow, it is of course important, when fighting forest fires, to establish firelines having a several foot width from which all vegetation and burnable material has been removed. Being able to establish and maintain such lines rapidly greatly enhances the ability of those fighting a forest fire to retard and control the spread of such fires. It is also important to employ a fireline plow that is towable by a tractor, such as a crawler type tractor shown in this application, and one that can be easily maneuvered to follow the tractor along a winding course through the forest. With tree forms increasing in numbers, it has been desirable to have a narrow fire plow that can be pulled between rows of young trees, spaced closely together and one that can be pulled by small tractors. In order to establish a clean and thus establish a fireline in these new environments, it is important that the fireline plow develope a narrow fireline, be maintained in plowing contact with the ground, but, at the same time, avoid unplowable objects in the soil such as tree roots without damaging the plow. Following the avoidance of such obstacles, it is important that the plow be returned to its plowing position as rapidly and effectively as possible.
Fire plows have existed for many years and are generally comprised of a main frame, supported for transport by an axle and at least one pair of wheels mounted in a support frame. This axle is connected to the plow's main frame by some type of height adjustment arrangement, such as a hydraulic cylinder with the height being adjusted either by moving the plow frame relative to the support frame and wheel axle or by swinging the axle to lower the support frame. The plow main frame also generally supports a rolling coulter blade, a middle buster plow, a pair of discs and a spreader bar welded at the tail end of the plow frame. These fireline plows have been very large and wide and had to be pulled by large tractors. Further, the discs were mounted outboard of and not directly on the main frame. This was necessary to be properly positioned outside of the middle buster plow and to develop the wide trench. Also, the rolling coulter blade would be mounted in a fixed position, relative to the main frame, and was not adjustable.
Fireline plows, as well as tractor hitches have existed in the art. One example of the combination is set forth in Brazell, U.S. Pat. No. 3,731,750. Brazell discloses primarily a hitch attachment which can affect the raising and lowering of a fireline plow comprised of a rolling coulter followed by a plow blade and a disc unit, all of which are attached to the plow's main frame. The hitch employs a hydraulic cylinder for raising and lowering the plow and when raised, uses a pin on the pivoting portion to control the position of the hitch and plow and to hold the plow centered. During raising, the pin will initially move between two sloping caming surfaces. As the pin moves along one or the other of the sloped surfaces, the hitch and that attached plow will be centered. When fully raised, the pin will lie between two vertical faces which are spaced apart just wide enough to receive the pin. This holds the plow in a centered position and also limits horizontal sway of the hitch. If the pin should wear, break off or otherwise become misformed, both the centering and the retaining functions would not operate precisely as desired.
In addition, a series of holes are provided in the hitch frame together with a separate pin so that when the hitch is in its raised position, that separately stored pin can be placed through the holes provided therefor in the hitch to lock the pivoting portion and prevent downward rotation around a horizontal axis. This pin, however, can only be inserted by an operator standing next to the hitch and not from any position on the tractor. Likewise, to remove this pin requires the tractor operator to be next to the hitch frame. Thus, this locking function cannot be achieved either automatically or from the driver's position on the tractor.
Noblin, U.S. Pat. No. 2,990,632, discloses a fire plow attachment for tractors. It is mounted ahead of the tractor and employs a forward nose section that has plow-like side plates for moving debris to opposite sides of the path and to lift logs and other debris out of the way. There then follows a coulter blade mounted in the center of a rolling drum and that is in turn followed by a clearing plow blade for scraping the surface of the ground that has just been rolled. The coulter is provided to cut small debris in advance of the rolling drum and material that cannot be cut by that coulter will cause the coulter to raise up over the debris simultaneously raising the following scraping plow blade to prevent it from engaging such debris. Noblin states that the purpose of his rolling drum is to regulate the height of the scraping or clearing plow.
Pendergast, U.S. Pat. No. 1,491,168 and Flynn, U.S. Pat. No. 2,582,538, relate to trenching machines for forming trenches, but do not contain or suggest the particular plow structures set forth herein. Reference can also be made to other patents which show various types of plows including Horner, U.S. Pat. No. 709,601, Domries, U.S. Pat. No. 2,852,995, Mikhailov et al, U.S. Pat. No. 3,510,970, Heiberg, U.S. Pat. No. 3,571,956, Jackson, U.S. Pat. No. 3,586,111, and Ruozi, U.S. Pat. No. 4,015,667.
In addition, Vink, U.S. Pat. No. 4,026,225, shows a machine for planting trees and shrubs and employs an initial cutting or ground loosening device provided with teeth which is followed by a pair of discs which further loosen the soil in the trench area. The discs are followed by a two sided trench coulter for digging the trench itself. This is followed by a tree planting section and finally by plates which return the soil originally dug from the trench back into the trench and around the trees being planted. Finally, Nja, U.S. Pat. No. 3,486,566, discloses a tractor plow that includes a stone release mechanism with the plow being pivotally mounted so that it can swing upwardly against the counter action of an overcenter spring mechanism. A compression spring surrounds each of a pair of parallel spaced rods, the springs being compressed by the upward pivoting as might be caused when an obstacle in the ground is struck by the plow. The increasing downwardly directed compressed spring force will endeavor to bring the plow back to its correct working position with the springs asserting approximately no force while the plow is in its normal working position.
With respect to the locking concept, attention is also directed to Bernotas et al, U.S. Pat. No. 3,527,308 which shows additional use of a pin and lever arrangement for holding a hitch assembly in a raised transport position. Anti-sway mechanisms can also be found in Wier et al, U.S. Pat. No. 3,047,076, Mellen, U.S. Pat. No. 3,107,736 and Van Der Lely, U.S. Pat. No. 3,223,177.
Andersen, U.S. Pat. No. 4,316,511, discloses the use of two latch members, one for holding pivoting arms on harrows or mowing machines in their raised transport position and in their lowered working position. Other forms of locking arrangements are also shown in Ruddock, U.S. Pat. No. 2,362,407, Jones, U.S. Pat. No. 3,274,712 and Orthman, U.S. Pat. No. 4,074,766.